Chemical metallization and products produced thereby



Aug. 27, 1968 F. w. SCHNEBLE; JR.. ET 3,399,268

CHEMICAL METALLIZATION AND PRODUCTS PRODUCED THEREB'Y Original FiledAug. 22, 1962 FlG.-l FIG.- 2

FIG."3

V J I L ,0

W I: I %A INVENTORS FREDER W. SCHNE E, JR JOHN McCORMA RUDOLPH J. ZEBLISKY JOHN DUFF W! A ON JOSEPH POLIC T United States Patent fice3,399,268 CHEMICAL METALLIZATION AND PRODUCTS PRODUCED THEREBY FrederickW. Schneble, Jr., Oyster Bay, John'F. Mc- Cormack, Roslyn Heights,Rudolph J. Zeblisky, Hauppague, John D. Williamson, Miller Place, andJoseph Polichette, South Farmingdale, N.Y., assignors, by mesneassignments, to Photocircuits Corporation, Glen Cove, N.Y., acorporation of New York Continuation of application Ser. No. 404,302,Oct. 16, 1964, which is a division of application Ser. No. 218,656, Aug.22, 1962, now Patent No. 3,259,559. This application June 7, 1966,SenNo. 555,918

The portion of the term of the patent subsequent to June 25, 1980, hasbeen disclaimed 18 Claims. (Cl. 174-685) ABSTRACT THE DISCLOSURE Theinvention is directed to novel articles of manufacture comprising anagent catalytic to the reception of electroless metal which catalyticagent is dispersed throughout an insulating material, said insulatingmaterial forming a coating for a suitable substrate and/or comprisingthe substrate itself and having tenaciously adhered to said coating orsubstrate a conducting metal layer and/or a bright, ductile,electrolessly deposited metal.

This invention relates to novel and improved methods for metallizinginsulating supports and to the products which result from such methods.

More particularly, the present invention relates to imposing by chemicalmeans strongly adherent and rugged deposits of metal on insulatingsupports and to the products which result from such methods.

Although applicable whenever it is desired to strongly adhere a metalcoating to an insulating base, as for example, for decorative efifect,or to make electrical conductors of a wide variety of shapes andconfigurations, the procedures for metallization disclosed herein areparticularly useful for making printed circuits from cheap, low-grade,readily available electrical insulating base materials or base materialscoated with electrical insulation materials,

This application is a continuation application of US. application Ser.No. 404,302, filed Oct. 16, 1964 and now abandoned, which application isa divisional application of US. application Ser. No. 218,656, filed Aug.22, 1962, now U.S.P. 3,259,559, and is a continuation-in-part ofco-pending applications Ser. No. 785,703, filed Jan. 8, 1959, nowabandoned; Ser. No. 33 ,361, filed May 31, 1960 now U.S.P. 3,146,125;and Ser. No. 26,401, filed May 3, 1960 now U.S.P. 3,095,309.

It is a primary object of the present invention to provide improvedchemical methods for imposing a uniform, rugged, firmly adherent,non-porous, bright and ductile deposit of copper on an insulatingsurface.

Another object of the invention is to provide chemical methods forimposing such a deposit of copper on irregularly shaped, complex, orcurved insulating surfaces.

Still another object of this invention is to provide improved chemicalmethods for imposing a rugged and adherent conductor pattern on cheap,readily available insulating base materials A further object of thisinvention is to provide improved printed circuits which are rugged anddurable, and which can withstand rough mechanical handling and heatshock.

Another object of this invention is to provide methods for makingimproved printed circuits in which the sup- 3,399,268 Patented Aug. 27,1968 port for the circuits has improved insulating properties. Anadditional object of this invention is to transform cheap, insulatingbase materials into commercially attractive electrical conductivecomponents by chemical means.

Other objects and advantages of the invention will be set forth in partherein and in part will be obvious herefrom or may be learned bypractice with the invention, the same being realized'and attained bymeans of the steps, instrumentalities and combinations pointed out inthe appended claims.

The invention consists in the novel parts, constructions, arrangements,combinations and improvements herein shown and described.

The accompanying drawings referred to herein and constituting a parthereof, illustrate embodiments of the invention and together with thedescription serve to explain the principles of the invention. Althoughthe invention will be described with particular reference to printedcircuits, and although fabrication of printed circuits constitutes aprimary and preferred application, it should be understood that the invention is not limited to printed circuits but is applicable tometallizing insulating surfaces broadly.

Heretofore, it has been suggested to manufacture printed circuits byprinting on an insulating backing a design of the circuit by means ofvarious inks containing receptive particles and then electrolesslydepositing a conductive material on the receptive particles.

Two main problems have been encountered in such a procedure. The firstproblem concerns the adhesion between the receptive particles and thebase. Techniques previously described include seeding a base materialwith aqueous acidic solutions of precious metal ions such as palladiumchloride. For example, the insulating material may be immersed in a bathcomprising an aqueous acidic solution of stannous chloride and palladiumchloride to render selected areas of the insulating material sensitiveto the reception of an electroless metal deposit. Such sensitizationbaths, however, have many disadvantages. First and foremost, theadhesion between the precious metal deposit and the subsequentlyelectrolessly deposited metal has been found to be tenuous. As a result,when the resulting circuits are subjected to rugged mechanical handling,or heat shock, such as by dip soldering, there is a tendency for theconductive layer to crack or pop free of the base, thereby disruptingthe circuit. Additionally, such treating solutions are ponderous andexpensive to employ, and must be carefully regulated if good results areto be achieved.

The second problem encountered in metallizing insulating bases by thetechnique under discussion resides in the electroless metal bath.Heretofore, a wide variety of electroless metal plating bath processeshave been proposed for the deposition of thin layers of metal uponinsulating surfaces, ceramics, plastics, and other materials. Ingeneral, none of these have been useful to any substantial degree forthe electroless deposition of copper on metal surfaces. The prior artbaths have produced copper deposits which are brittle, break undervibration and bending, and otherwise exhibit p'oor ductility, althoughmany of the baths are commercially useful within recognized limits.Additionally, the deposits produced by most prior electroless copperdepositing baths do not produce copper deposits which are bright.Rather, the

- deposits from conventional baths ordinarily exhibit a dull surface'ofpoor color. Frequently, the prior art baths yield a muddy layer ofcopper. Additionally, the baths of the prior art processes are oftensubject to instability, and impurities rapidly accumulate in the baths,the bath finally reaching a condition such that it spontaneouslydecomposes, throwing out copper as a useless precipitate.

' These and other disadvantages of the prior art are over-.

come by the present invention.

According to this invention, a process for metallizing insulatingsufaces has been discovered which comprises providing an insulating basematerial with adhesively bound, finely divided, solid particles of anagent catalytic to the reception of electroless deposited metal, andthen subjecting the resulting base material to a new and improvedelectroless copper bath to be disclosed.

When'the catalytic compositions and the electroless depositing bathsdescribed herein are employed in the manner and in the sequence to bedescribed, there is produced onthe base material a dense, uniform,ductile, bright, conductive copper deposit which is firmly. andtenaciously adhered to the. base material or substrate. I a 'It is thecombination of the catalyticcomposition to the electroless copperdepositing baths disclosed herein that leads to the production of newand unexpectedly improved coatings of copper on an insulating base.

When the catalytic composition and the electroless copper depositingbaths disclosed are employed in making printed .circuits, manyadvantagesover the conventional commercial procedures are obtained. According tothis process, copper is applied only where desired. No etching isrequired, and no copper is thrown away. The process is readily adaptableto mass production techniques, and miniaturized circiuts having firmlyadherent conductive patterns are obtained. Additionally, the copperdeposit forming the conductive pattern is ductile and bright, and itsthickness can be controlled to close limits. The fact that the copperdeposit is ductile is highly significant. Because of its ductility, theconductor pattern is strongly resistant to both mechanical and thermalshock and can readily withstand both rough mechanical handling andsoldering, including dip soldering. Heretofore, so far as applicants areaware, it has not been possible to deposit a ductile copper layer usingelectroless techniques. Additionally, the process is economical andrequires a minimum amount of control. Further, the copper deposit can beapplied on practically any base material, regardless of size, shape orconfiguration, and can be subsequently readily coated or reinforced withother metals by electroless dip techniques or other procedures to impartspecial characteristics or properties to the circuits as a whole, orportions thereof.

A limiting factor in the production of printed circuits by theconventional print and etch technique is that the thickness of the foil,ordinarily produced by rolling copper, has a lower limit of about 0.7 to1.3 mils. Frequently, for special purposes, it is desirable to have aconductor pattern which is less than 0.7 mil., i.e., in the order ofabout 0.1 mil. or even lower. With the techniques described herein,uniform layers of ductile copper having a thickness of less than 1.3mils, or in the order of about 0.1 :mil to 7 mils, or even less, mayreadily be achieved.

The catalytic compositions forming a part of the present inventioncomprise an adhesive resin base having dispersed throughout finelydivided particles of an agent which is receptive to electrolesslydeposited copper.

The receptive agents dispersed throughout the resin base are cheap,readily available, particulate, finely divided metal or metal oxides,such as titanium, aluminum, copper, iron, cobalt, zinc, titanous oxide,copper oxide, and mixtures of the foregoing.

Particularly good results are achieved when the receptive agent iscuprous oxide and this material is preferred for use. Cuprous oxide isitself an exceptionally good insulator of electricity. Additionally,when reduced, as by treatment with an acid, the cuprous oxide may bechanged to metallic copper to initially form the conducting portion ofthe desired printed circuit design which may then be further built up byelectroless deposition by immersion or otherwise treating with theelectroless copper depositing baths to be disclosed.

The'cataly tic compositions of the present invention may take a varietyof forms.

For example, the insulating base members contemplated for use are mostfrequently formed of resinous material. When this is the case, theactive agent disclosed herein, and especially'copper oxide, in finelydivided, form, may be incorporated into the resin b ymilling,calendering,"or' other conventional methods after which the resin is setto form thebase. 4

Alternatively, thin film or' strip or unpolymerized resin havingparticles of the active agent suspended therein 'rnight belaminated to21v resinous insulated base and 'cured' thereon. In this embodiment, theinsulating base could be ;a resin impregnated laminate vof paper orcloth sheets orFiberglas.

In the preferred embodiment an ink comprising an adhesive resinousmaterial having dispersed therein finely divided particles of thecatalytic agent is printed on the surface of an insulating supportandcured thereon.

Regardless of the manner in which it is incorporated in or on the basematerial, the catalytic agent is present in a finely divided form andpreferably passes 200 mesh, US. Standard Sieve Series. Ordinarily from asmall fraction of 1% to about of the active agent is admixed withadhesive resinous material to form the catalytic composition, but thisconcentration will depend to a large extent upon the materials used, andupon the time in which the catalytic compositions are allowed to remainin the electroless plating bath.

The resins into which the particles of the active material are dispersedpreferably comprise, in combination, a thermosetting resin and aflexible adhesive resin. Typical of the thermosetting resins may bementioned oil soluble phenolic type resins, such as fusible copolymersof phenol, resorcinol, a cresol, or a xylenol with an aldehyde or withfurfural. Also may be mentioned the polyester resins, which are wellknown in the art and are prepared by reacting dicarboxylic compoundswith dihydric alcohols, for example, by the reaction of phthalic ormaleic anhydride with' mono-, di-, or polyethylene glycols. Thepolyester resins are ordinarily dissolved in styrene monomer andcross-linked by reaction with the styrene. As the thermosetting resinmay also be mentioned epoxy resins, such as the reaction product ofepichlorohydrin with bisphenol A. 7

Typical of the flexible adhesive resins are the epoxy resins, polyvinylacetal resins, polyvinyl alcohol, polyvinyl acetate, and the like. Alsoas the adhesive-resin may be mentioned chlorinated rubber and butadieneacrylonitrile copolymers.

Theadhesive resins of the type described have appended thereto polargroups, such as nitrile, epoxide, acetal, and hydroxyl groups. Suchadhesive resins copolymerize with and plasticize the thermosettingresins, and impart good adhesive characteristics through the action ofthe polar groups.

The thermosetting resin portion of the composition is required in orderto afford resistance to heat upon soldering, and also to protect againstdecomposition when subjected to the electroless copper bath. Athermosetting resin alone, however, will not ordinarily have adequatetackiness or sufficient flexibility to resist heat shock; and

. would have negligent resistance to peeling of long conductor patternsfrom the surface. Admixture of adhesive resins such as those disclosedovercome the deficiencies of the thermosetting resins, and together, thethermosetting and adhesive resins provide an especially suitablecomposition for carrying the catalytic agents and for adhesively bindingthem to the base.

Particularly suitable for use as the adhesive resin for certainsubstrates is a combination of a phenolic type resin and an epoxy resin.The most common epoxy resins for use in the resinous composition arecopolymers of epichlorohydrin (l-chloro-2,3-epoxy propane) withbisphenol A (2,'2,-p-hyd'roxy phen'yl propane) which have melting pointswithin the range of 20 F. to 375 F. and molecular weights of about350'to l5,000. 1

Although epichlorohydrinis the 'most important organic epoxide "employedin the formation of the epoxy resins, other epoxides such as,- forexample,..1,2,3,4-dipeoxy butane .may be used. Similarly, epoxy resinsderived from phenols other than bisphenol A are suitable for use. Suchresins include, for.example, thereaction product ofepichlorohydrin'with' resorcinol, with phenols derived from cashew.nut.oils, with hydroquinone, with 1,5.-dihydroxy vnaphthalene or with2,2,5,5-tetrabis-(4- hydroxy phenyl) hexane. Phenolic intermediates ofthe resol type, hydrazines and sulfonamides, such as, for example,-2,4-toluene disulfonamide, may also be used for reaction with anorganic epoxide to produce epoxy resins suitable for use. Aliphaticepoxy resins are also suitable. Such resins are, for example, thereaction product of epichlorohydrin with glycerol, withethylene glycolor with pentaerythritol. i

The phenolic type resin maybe a copolymer of a phenol, resorcinol, acresol or a xylenol with an aldehyde or with furfural. Thus, it may be acopolymer of phenol or a substituted phenol with formaldehyde or aformaldehyde-yielding material, suchas, paraformaldehyde orhexamethylene tetra-amine, The phenolic resin is preferably of the oilsoluble type. As examples of thermosetting phenolic type resins whichmay be used may be mentioned copolymers of formaldehyde with p-cresol,p-ethyl phenol, p-tert butyl phenol, p-tert amyl phenol, p-tert octylphenol, p-phenyl phenol, di-isobutyl phenol, or a bisphenol, such as4,4-isopropylidene diphenol or 2,2- bis (p-hydroxy phenyl) propane. Itmay be of the modified type, such as, for example, one which has beenmodified with copal or rosin to cause it to be oil soluble.

The phenolic type resins are, themselves, curing agents for the epoxyresins, and even those which are, themselves, permanently fusible form atough, adherent film in combination with an epoxy resin which isprobably the result of a cross-linking between the epoxy resin and thephenolic type resin. However, the resinous compositions may contain anadditional curing agent. This curing agent maybe another resin, such as,for example, a polyamide resin or a melamine-formaldehyde resin, or itmay be, for example, a dibasic acid, such as, for example, phthalicanhydride, an amine, such as, for example triethanolamine, diethylenetriamine or metaphenylene diamine, or an amide, such as, for example,dicyandiamide.

When using a thermosetting type of phenolic resin, a curing agent forthe phenolic, such as, for example, one of the'amines mentionedhereinabove as 'a curing agent for epoxy resin may be employed. 7

The active. agent it should be clear, is incorporated into the resinouscompositions in such a way that the agent is dispersed throughout theresin, and present in the resin, jupon solidification, at numerousindividual sites. Because of this dispersion, the particles of thereceptive agents are not in contact with one another and accordingly,the catalytic compositions disclosed herein are non-conducting. Ofcourse, when the active agent is itself non-conducting, such as cuprousoxide, or titanous oxide, this factor is not important. When metals suchas copper, iron, and so forth, are employed as the active agent,however, the dispersion of the active particles throughout the resinbecomes important. Were conducting particlesto be incorporated into thecatalytic compositions in such a manner that they were in intimatecontact with one another, it would be impossible to prepare printedcircuits from such compositions using the socalled reverse, method. Inthis method, the catalytic composition would be adhered to the over-allsurface of the base material or the base material would itselfconstitute' the catalytic composition, and selected portions thereofwould then be masked, leaving exposed the conductor pattern. The basewould then be immersed in the electroless copper bath to deposit copperon the exposed areas. Were the catalytic composition employedconductive, leakage would occur between the lines of the conductorpattern through the catalytic composition. Obviously, such a situationcould not be tolerated.

When large amounts of the active agent are employed, as compared to theresin, relatively small amounts of resin bind the uppermost or surfaceparticles of the active agent. Accordingly, electroless copper canreadily deposit on the active agent on the surface. When small amountsof the active agent are employed in comparison to. the resin, e.g., 0.25to 10% by weight, it may be that the active agent at the surface of thecatalytic composition will be completely coated by the resinousmaterial. In this situation, it may be necessary to abrade the surface,so that the particles will be exposed to the electroless plating bath.If, in this situation no abrasion is used, it will be necessary toexpose the surface to theelectroless plating bath for several hoursbefore the initial copper deposit will form.

When copper oxide is used, it is preferable to activate the cuprousoxide by treatment with an acid, to convert at least a portion of thecuprous oxide particles at the surface of the ink to copper. Preferredfor use is sulfuric acid. Other reducing agents which are acceptableinclude aqueous solutions of phosphoric acid, acetic acid, sulfuricacid, hydrofluoric acid, dithionates, hypophosphites, and the like.Nitric acid may also be used but it is not quite as desirable as theothers since it dissolves the copper formed at a rather high rate.Alkaline formaldehyde solutions including the electroless copper bathsdisclosed herein will also reduce the cuprous oxide. 7

Among the wide variety of adhesives which may be used when it is desiredto prepare the catalytic compositions in the form of inks are thosecompositions disclosed in US. Patent Nos. 2,532,374 and 2,758,953. Inthis embodiment, the receptive agent, as will be clear, is imparted intothe adhesive base in such a way that the receptive agent is dispersedthroughout the base medium, and present in the base medium at numerousindividual sites.

Typical examples of catalytic inks suitable for use in printingconductor patterns on an insulating base are given below:

EXAMPLE 1 Xylene 50 Diacetone alcohol 75 Parlon l0 cps. 50Phenol-formaldehyde (oil soluble) 10 Butadiene-acrylonitrile rubber 20Cab-O-Sil 3 Cuprous oxide 70 Example 2 Butadiene acrylonitrile rubber15.5 Diacetone alcohol 72 Nitromethane 72 Phenol-formaldehyde resin (oilsoluble) 7.5 Cab-O-Sil 4 Ethanol 3 Parlon 10 cps. 10 Xylene 50 Cuprousoxide Example 3 Butadiene acrylonitrile rubber 15.5 Diacetone alcohol 50Nitromethane 50 Phenol-formaldehyde resin (oil soluble) 7.5 Parlon 10cps. 3 Toluene 20 Cab-O-Sil 3 Ethanol 3 Cuprous oxide 60 EXAMPLE 4Butadiene acrylonitrile rubber 15.5 Diacetone alcohol 50 Nitromethane 50Phenol-formaldehyde resin (oil soluble) 7.5 Cab-O-Sil 3 Ethanol 3Cu'p'rous oxide 60 EXAMPLE 5 Toluene 50 Diacetone alcohol 50 Butadieneacrylonitrile rubber 10.5 Phenol-formaldehyde resin (oil soluble) 7.5Parlon cps. 5 Ethane-1-..; 5 Cab-O-Sil 6 Cuprous oxide 50 EXAMPLE 6Epoxy resin Butadiene acrylonitrile rubber 15 Diacetone alcohol 50Toluene 50 Phenol-formaldehyde resin (oil soluble) 11 Cuprous oxide 60In the above examples, Parlon is a chlorinated rubber from HerculesPowder Company. The epoxy resin of Example 6 is DER 332, sold by DowChemical Company, and is the reaction product of epichlorohydrin andbisphenol A. It has an epoxy equivalent of 173 to 179', an averagemolecular weight of 340* to 350 and a viscosity, at 25 C. of 3600 to6400. Cab-O-Sil is a trade name for silica aerogel.

To prepare the coating compositions or inks disclosed in Examples 1 to6, the resins are dissolved in the solvents and milled with the pigmentson a three roll mill.

The viscosity of compositions having the formulae of Examples 1 to 6will ordinarily vary between about 5 and 100 poises at C.

The catalytic inks may be applied to the panel in my convenient manner.For example, when a direct process for making printed circuits isemployed, the circuit pattern of the ink may be imposed on theinsulating base by screen printing or offset printing techniques. Whenthe reverse process is employed, the insulating base may be coated withthe catalytic ink, as by dipping, spraying, calendering, and the like,and then portions thereof masked to leave exposed the conductor pattern.When the catalytic inks are used to produce plated through holes, theink may be drawn into the holes by vacuum. Alternatively, the piercedpanels may be dipped into the inks, and then vibrated to remove excessink from the holes.

After treatment of the panel with the catalytic ink, the adhesive baseof the ink may be partially or fully cured by heating, thereby firmlybonding the adhesive ink with its contained receptive agent to theinsulating base member.

The insulating base materials used to make the printed circuits must beable to withstand the temperatures which will be encountered inprocessing and in use. Preferable for use as insulating base materialsare sheets of ceramic, phenol-formaldehyde, melamine-urea, vinylacetate-chloride copolymer, rubber, epoxy resin polymers, epoxyimpregnated Fiberglas, and the like.

After curing, the catalxtic ink may be lightly abraded by rubbing itssurface with steel wool, sand paper or other abrasive material so thatthe receptive particles which make up the active sites are exposed. Asindicated hereinabove, this step is not always necessary and depends toa large extent upon the exact nature of the adhesive compositionemployed in the ink and upon the concentration of the receptiveparticles in the ink.

Electroless plating baths preferred for use in the present inventionconsist essentially of a soluble copper s'alt (e.g., copper sulfate,cupric chloride, cupric nitrate, copper gluconate, cupric acetate, "andthe like) g a complexing agent for the cupric ions (e.g., Rochellesalts;-ethylene diamine tetraacetic acid and its sodium salt;nitrolotriacetic acid and salts thereof; N-hydroxyethylethylenediaminetriacetate; triethanolamine; sugar, including sucrose, dextrose,lactose, levulose or maltose; mannitol; sorbitol gluconic acid and thelike); an alkali or alkaline earthmetal hydroxide, such as sodium. orpotassium hydroxide; an active reducing agent such as formaldehyde; anda small amount of a complexing agent forcuprous ion, suchnas cyanidesalts, e.g., sodium and potassium cyanide, acrylonitrile, lactonitrile,glyconitrile; thiourea, allyl alcohol, and ethylene. Preferred for useas the com plexing agent for cuprous ion are the cyanide salts, such assodium and potassium cyanide, acrylonitrile, lactonitrile, andglyconitrile. t The quantities of the various ingredients in the bathare subject to wide variation, within-certainranges which may bedefined-as follows: Y

Copper salt from 0.5 g. to saturated solution (0.002 to .15 mol. ormore).

Alkali metal hydroxide to give pH 10.5 to 14.

Formaldehyde 0.06 to 3.4 mol.

Complexing agent for cupric ion 0.5 to 2.5 times moles of copper. Y

Complexing agent for cuprous ion (0.00002 mol. to

0.06 mol.).

Water-sufficient to make 1 liter.

The ratio of the copper salt to the complexing agent for cupric ionshould be such that there are from 0.5 to 2.5 as many moles of cupriccomplexing agent as of copper, e.g., 5 grams of CuSO 5H O requires from2.5 to 8.5 grams of Rochelle salts.

Sodium hydroxide and sodium cyanide are preferred over the correspondingmore costly potassium and other alkali metal salts, which are of greatermolecular weight.

Rochelle salts, the sodium salts (mono-, di-, tri-, and tetrasodiumsalts) of ethylenediaminetetraacetic acid, nitriltriacetic acid and itsalkali salts, gluconic acid, gluconates, and triethanolamine arepreferred as cupric ion complexing agents, but commercially availableglucono-fi-lactone and modified-ethylenediamineacetates are also useful,and in certain instances give even better results than the pure sodiumethylenediaminetetraacetates. One such material isN-hydroxyethylethylenediaminetriacetate.

Cupric sulfate is preferred as the copper salt, but other soluble coppersalts may be used, such as the nitrate, chloride and acetate.

In considering the general formulae for the electroless copper baths andthe specific working formulae which are set forth below, it should beunderstood, that as the baths are used up in plating, the' cupric salt,and the formaldehyde reducing agent may be replenished from time totime, and also that it may be advisable to monitor the pH and cuprousiOn complexing agent content of the bath, and to adjust these to theiroptimum value as the bath is used.

The baths are ordinarily used at slightly elevated temperatures, such asfrom 35 to 65 C. although many of them may be used at even highertemperatures. As the temperature is increased, it is usual to find thatthe rate of plating is increased, and that the ductility ofthe depositis increased to a slight extent, but the temperature is not highlycritical, and within the usual operating range, excellent deposits areproduced which exhibit greatly improved properties over those obtainedwith conventional baths.

With electroless copper plating baths used herein, the efiiciencyofcopper recovered by electroless deposition from the bath often exceedswhichis much greater The cuprous ion complexing agent in the bath isanim? portant 'featureand serves to prevent or minimize the formation ofcuprous oxide in the bath, and also appears to inhibit the formation ofresulting hydrogen in the electroless deposited metal. Without thecuprous ion complexing agent, e.g., cyanide and the like, the bath hasbeen found to be unsatisfactory as astable plating solution, and theelectroless copper deposit has been found to be smudgy and of a poorappearance on the surface opposite the adhering base. Additionally, ithas been discovered that without the cuprous ion complexing agent, aductile deposit of electroless copper is not obtained. I

The baths to be described herein will ordinarily deposit a coating ofelectroless copper of a thickness of about 1 mil., withinbetween about10 and 100 hours, depending on the composition, pH, temperature, andrelated factors.

Examples of the electroless copper depositing baths suitable for usewill now be described.

EXAMPLE 7 Moles/l. Copper sulfate 0.03 Sodium hydroxide 0.125 Sodiumcyanide 0.0004 Formaldehyde 0.08 Tetrasodium ethylenediaminetetraacetate0.036 Water Remainder This bath is preferably operated'at a temperaturev of about 55 C., and will deposit a coating of ductile electr o lesscop'perabout 1 mil. thick in about 51 hours. 1

Other examples of suitable baths are as follows:

This bath is preferably operated at a temperature of about 56 C., andwill deposit a coating of ductile electroless copper about 1 mil. thickin about 21 hours.

EXAMPLE 9 Moles/l. Copper sulfate 0.02 NaOH 0.125 NaCN 0.0002

HCHO 0.47 Rochelle salt 0.0425 Water Remainder EXAMPLE l- Moles/l Coppersulfate 0.04 NaOH 0.19

NaCN 0.0002

Rochelle salt 0.0425 HCHO 0.47 Water Remainder EXAMPLE 11 Moles/l.Copper sulfate 0.04 NaOH 0.19 NaCN 0.0006 HCHO 0.47 Rochelle salt 0.0425Water Remainder 10 EXAMPLE 12 Moles/l. Copper sulfate 0.04 Sodiumhydroxide 0.19 NaCN 0.0002 HCHO 0.47 Rochelle salt 0.064 Water RemainderEXAMPLE 13 Moles/l. Copper sulfate 0.02 NaOH 0.125 NaCN 0.0002 HCHO 0.40Sodium citrate 0.051 Water Remainder EXAMPLE 14 v v v Moles/l. Coppersulfate 0.02 NaOH 0.05 NaCN 0.0002 HCHO 0.1 Trisodium N-hydroxyethylenediaminetriacetate 0.024 Water Remainder The following examplesare illustrative of the improved methods of :making printed circuitsaccording to the teachings contained herein.

EXAMPLE 15 An insulating base is formed by uniformly mixing grams ofCiba 6005 which is the reaction product of bisphenol A andepichlorohydrin which has a viscosity of 4500 centipoises and an epoxyequivalent of and adding to it an equal weight of cuprous oxide whichpasses 200 mesh and milling with the pulverulent copper oxide particlesfor 1 to 2 minutes, which makes for a mixture which is relativelyuniform. This uniform mixture is ready for immediate use or may be setaside for later use. It has an amine hardener, in this case 70 grams ofdiethylene triamine blended with it by constant turning, cutting andrubbing for about 2 minutes. It is then transferred to a mold by meansof which it is given the shape desired. Heat may be applied to speedsetting of the epoxy resin loaded with cuprous oxide particles so thatthe reaction is complete in a period of about one hour.

One surface of the insulating base thus formed is pro-' vided with aresist, portions of which have been removed, said portions masking outthe circuit design which it is desired to form. An aqueous solution of30 Baum sulfuric acid is then applied to the resist covered surface. Thestrength of the acid is not particularly critical and acid strengths offrom 5 to 40 Baum have proven quite acceptable. The acid is allowed toremain in contact with the resist covered surface for 10 minutes.Contact of from 5 to 15 minutes is the usual period of time in which thecuprous oxide particles which are unprotected by the resist are reactedupon by the acid and converted to metallic copper. The acid is thenremoved by a thorough rinsing and the insulating base is then immersedin the electroless copper bath of Example 7 for about 51 hours. Auniform, adherent, bright, ductile cop per deposit about 0.001 inchthick was built up during this period of time. The deposit wastenaciously adhered to the base and could only be removed by scraping.The deposit could be readily soldered, both by dipping in a hot solderbath, and by hand soldering.

EXAMPLE 16 Since only the surface portion of the insulating base isacted upon during the contact with the acid it has proven desirable insome cases to take a cuprous oxide loaded resin and coat the surface ofan insulating support with a lamina of such a composition and cure itthereon. A coating of epoxy resin-cuprous oxide as described in Exampleis applied to a clean urea-formaldehyde resin support to a depth ofabout of an inch and cured thereon. This depth may be varied on eitherside of that used here but of an inch is the most useful for anypractical purpose. After curing this lamina thereby bonding it to theinsulating base substance, the other steps of the process, i.e.,masking, developing with acid and electrolessly plating, are carried outas in Example 15, and comparable results are obtained.

EXAMPLE 17 per deposits on the lateral sides surrounding the holes' as.well as on the circuit design. As will readily be apprech ated, thistechnique affords an extremely simple and facile method of makingprinted circuits with plated through holes.

The cuprous oxide loaded base of Example 15 also permits formation ofprinted circuits in a solid block of insulating material, as will beclear from the following examples.

EXAMPLE 18 A cylindrical block of cuprous oxide loaded resin wasprepared following the procedure of Example 15. The surfaces of thecylindrical block are then covered completely with a resist. Holes arethen drilled into the cylindrical block to form a pattern ofinterconnecting channels. Drilling the holes exposes the catalytic agentat myriad individual sites on the walls defining the holes. Thecylindrical block is then treated with acid and immersed in theelectroless copper bath, as described in Example 15. An adherentuniform, bright, ductile copper deposit is thereby formed on the lateralwalls of the holes to form a printed circuit which is entirely encasedin the cylindrical block.

If desired, of course, a circuit pattern could also be imposed on theexterior surfaces of the block. The conducting pattern on the surfacecould connect or not connect with the circuit in the interior of theblock.

The importance of such a technique in forming microminiature circuitswill readily be apparent to those skilled in the art.

In Examples 17 and 18, the solid block of material used to form theprinted circuit could of course be any geometrical shape, such asspherical, tetragonal, hexaonal and the like.

EXAMPLE 19 Parts Phenol-formaldehyde resin (alcohol soluble) 60Polyvinyl butyral resin 40 Ethanol 100 Cuprous oxide (powder, pass 200mesh) 150 Powdered silica (methyl isobutyl ketone), sufficient to adjustviscosity to about 200 poises.

The resin-based ink circuit thus outlined is cured, bonding it to theresin insulating base. The cuprous oxide particles are reduced tometallic copper by means of contacting the cured resin-based inkcontaining cuprous ox- 1'2 ide particles with an acid and building upthe circuit in the same manner as in Example 15.

If plated through holes are desired, these may be achieved by piercingthe insulating base support prior to or following printing, and coatingthe lateral walls surrounding the holes with the catalytic ink, andcuring. The panel is then treated with the acid an d then ,with theelectroless copper bath to deposit copper on the con: ductor patternandon'the lateral walls surrounding the holes. i V

. EXAMPLE 20 An adhesive containing a small amount of copper oxide (CuO) is prepared as follows: j Y

Partsbyweight Butadiene-acrylonitrile copolymer 1 23-Phenol-formaldehyde resin 2 10 Zirconium silicate 107 Silica (20) 4Cuprous oxide 0.5 Isophorone Xylene 31 1 Medium high acrylonltrllecontent.

Combination of 5 parts oil soluble, heat reactive, solid resin, M.P.144-162" F. and 5 ble, heat reactive. solid resin.

The rubber is dissolved in part of the solvents and the phenolicresin'dissolved separately in the rest of the solvents. The twosolutions, cuprous oxide and the pigments are blended in a three rollpaint mill. The circuit design is screen printed with the resulting inkon an epoxy-impregnated Fiberglas laminate and cured. The cured print ofthe circuit is immersed in 20 Baum sulfuric acid solution for 10minutes. It is then removed, Washed free of sulfuric acid and immersedin the electroless plating bath described hereinabove. Again, platedthrough holes may be formed, if desired, using the procedure of Example19.

EXAMPLE 21 The epoxy resin, cuprous oxide and pigments are blendedtogether in a three roll paint mill, and the polyamide resin was warmeduntil readily workable and blended with the mixture from the mill byconstant turning, cutting and rubbing for 5 minutes. The mix was cast ina mold and cured at 250 F. for 45 minutes. The fabrication of theprinted circuit was carried out as in Example 1.

, EXAMPLE 22 Examples 15 to 21 are repeated with comparable resultsusing finely divided particles of titanium, aluminum, copper, iron,cobalt, zinc and titanous oxide as the catalytic agent. With theseagents, the acid treatment was not necessary. Best results were achievedwhen the catalytic composition was slightly abraded prior to exposure tothe electroless copper bath.

EXAMPLE 23 Holes are drilled in a cylindrical block of acrylic resinhaving a diameter of 4 inch and a height of 1 inch. The holes aredrilled at various angles and various direcparts alcohol soluble, oilso1u-.

tions so that they interconnect each other at selected positions, asshown, for example, in FIGURE 4.

v The holes are cleaned by treating with a mild alkaline cleaner, andthen the holes are coated with the catalytic ink of Example 1. Residualink is removed from the surface of the cylinder. The cylinder is thentreated with acidand immersed in the electroless copper depositingbath.An adherent, bright, ductile copper deposit is formed on lateralwalls surrounding the holes to form a printed circuit completelyencapsulated with the cylinder of acrylic resin.

The particular amounts of catalytic agent shown as specific examplesherein are operable, although the preferredamounts for obtaining a rapidelectroless deposition while using a reasonable amount of catalyticagent is between and 20% by WeightLThe initial copper depositionobtained with these amounts occurs within about 2 to 10 minutes afterimmersion in the electroless plating bath.-

The following figures are included to illustrate the. major embodimentsof the catalytic compositions disclosed herein. 7

FIGURE 1 shows an insulatnig base 1 which has randomly distributedthroughout it particles of cuprous oxide 2; FIGURE 2 shows an insulatingsupport 3 to which there has been laminated an insulating base 1 inwhich there is randomly distributed particles of cuprous oxide 2; 1FIGURE 3 shows an insulating support 3 having applied on its surfaceparticles of cuprous oxide 1 in the form of filler in an adhesive ink 4;FIGURES 4, 4a and 4b show an embodiment of a printed circuit in whichthe printed circuit pattern 6 is formed in holes'bored into a solid massof an insulating material 8, as described in Example 24; and

. FIGURE 4 is an isometric view of the circuit and FIGURE 4a is a crosssectional View showing how the interconnecting circuit pattern 6comprising the electroless copper deposit 10 runs through the insulatingma terial 8. FIGURE 4b is an enlarged cross sectional view of theconducting pattern of FIGURE 4a and depicts how the electrolessdeposited copper 10 is adhered to thecatalytic composition 12 which inturn is bondedto the lateral wall of insulating material 8 defining theapertlll'e 6. 1

,The FIGURES 1 to 3 show intermediate products resulting from thecarrying out of the methods described in the. corresponding examples inthe specification in that FIGURE 1 corresponds to Example 15, FIGURE 2corresponds to Example 16 and FIGURE 3 corresponds to Example 19.FIGURES 4, 4a and 4b are schematic illustrations of the printed circuitproduced according to the teachings of Example 23.

, As is, clear from the foregoing examples, the base materials on whichthe metal is deposited are capable of wide variation in composition andconfiguration. Among base materials to which the catalytic compositionmay be adhered may be mentioned impregnated laminates of paper or cloth,or even fiberglas. The resin impregnant for such laminates includephenolics, epoxies, polyesters, and the like. When impregnated laminatesare used, it is desirable to pre-coat the laminates with a smoothplastic film prior to adhering the catalytic composition. As is alsoclear from the foregoing examples, the base materials may include moldedplastic, such'as molded epoxy resin, polyester resin, epoxy resin, andthe like. The base materials may even have incorporated therein theactive agent for reception of the electroless copper deposit, as isclear from Example 15. In this embodiment, it is not necessary toseparately adhere the catalytic composition to the base material, sincethe base material, itself forms the blank from which printed circuitsmaybe made directly.

Still other possible base materials include lightweight syntheticmaterials well known to the building trade, such as wallboard, Masonite,Transite, and the like. Also may be mentioned anodized aluminum whichhas been sealed in a manner well known in the art to render the anodizedcoating insulating.

Also suitable for use as the base material are plastic coated metals,such as aluminum, anodized aluminum or steel coated with a resin. Suchplastic coated metals are well known in the art, and are commerciallyavailable. They may be prepared either by dip coating, spray coating, orflame coating metal, substrates with a resin. Preferably, however, sincesmooth surfaces are desired, such metal resin coated laminates areprepared by fluidized bed techniques which are now well known in the artand described, for example, in U .8. Patent 3,028,251.

Suitable compositions for use in fluidized bed coating of a metalsubstrate with an insulating coating of a plastic material comprise amixture of fusible epoxy resin and a fusible phenolic type resin. Thecompositions are in the form of free-flowing powders, which are fusibleat an elevated temperature below the temperature at which the resin willbe decomposed during the formation of the coating by fusion.Compositions in which the epoxy resin varies from about 10 to aboutbased upon the total weight of the two resins, are preferred. Thecoating composition may contain other types of resins in addition toepoxy resin and phenolic resin, such as, for example, a polyester resin,a polyamide resin, a melamine formaldehyde resin or a natural resin,such as copal or rosin.

In the fluidized bed coating technique, finely divided solid particlesof the resin composition are fluidized in a stream of gas, such as air,and a pre-heated article to be coated immersed in the fluidized bed forsuitable periods of time. Following removal from the bed, the coatedarticle is heated to fuse the coating. The particles of resin in thefluidized bed will ordinarly range in size from about 5 to 600 mesh, US.Standard Sieve Series.

The following examples illustrate methods of forming printed circuitsusing plastic coated metal base materials.

EXAMPLE 24 Fifty parts, by weight, of an epoxy resin formed by thereaction of bisphenol A with epichlorohydrin and characterized by anepoxide equivalent (grams of resin containing one gram equivalent ofepoxide) within the range of 1550 to 2000, an equivalent weight or 190,a melting point of 127 C. to 133 C. and a particle size less than 40mesh, fifty parts, by weight, of a phenolic resin produced by thereaction of phenol with formaldehyde and characterized by a softeningpoint of F. to 220 F., a specific gravity of 1.2 and a particle sizeless than 40 mesh and two parts, by weight, of powdered silica having aparticle size ranging from 1 micron to 7 microns were dry blendedtogether.

A pierced and blanked aluminum plate having a thickness of 41 inch, awidth of about 3 inches and a length of about 6 inches was heated to atemperature of 400 F. and while at that temperature immersed in afluidized bed of the dry resin blend for a period of time ranging from Asecond to 2 seconds. Upon removal from the fluidized bed, the coatedpanel was maintained at a temperature of about 400 F. for a period ofabout 15 minutes to cure the coating which had been deposited thereon.Upon curing, the coating on the plate was found to vary from about 2 to10 mils. in thickness, depending upon the time of contact in thefluidized bed. The coating was semi-gloss transparent and showed thenatural color of the aluminum.

The coating extended through the plurality of holes in the panel. Theseholes had an original diameter of about 50 mils.

The resulting plastic coated aluminum was screen printed with thecatalytic ink described in Example 2 to form a conductor pattern. Thecatalytic ink circuit thus outlined was cured to firmly bond it to thebase.

The cuprous oxide particles in the catalytic ink were reduced tometallic copper by immersion in sulfuric acid following the procedure ofExample 15. The panel was then immersed in the bath of Example 8 for aperiod of about 36 hours, thereby building up a printed circuit in thesame :manner as in the previous examples.

Following electroless copper deposition, the panel was post cured byheating for about 2 hours at 130 C. In this embodiment, plated throughholes may be readily formed by coating the lateral walls surrounding theholes with the catalytic ink prior to acid treatment and immersion inthe electroless copper bath.

EXAMPLE 25 Example 24 is repeated with the exception that by weight ofcuprous oxide having a'particles size of less than 200 mesh, U.S.Standard Sieve Series, based on the weight of the resin, wasincorporated into the resinous composition prior to blending.

A pierced and blanked aluminum plate was anodized and coated with theresulting composition using the technique described in Example 24.

The plastic coating contained particles of cuprous oxide finelydispersed throughout. To form the printed circuit, the surface of thepanel was coated with a masking composition which left exposed aconductor pattern and also the lateral walls surrounding the holes. Thepanel was then immersed in sulfuric acid having the strength of aboutfor about 5 to 15 minutes to reduce at least a portion of the cuprousoxide to copper in the exposed areas of the conductor pattern and in theholes. The panel was then immersed in the electroless copper platingbath of Example 9 for about 75 hours, at the end of which time a firmlyadherent, ductile, and bright electroless copper deposit had built up onthe conductor pattern and on the lateral walls surrounding the holes.

In this example, the holes in the aluminum panel were coated by thefluidized bed technique, so that the holes actually had cuprous oxideparticles adhered to the lateral sides of the holes. The wallsurrounding the holes, in other words, following activation of thecuprous oxide with the acid, contained sites catalytic to electrolesscopper deposition. Accordingly, when the panel was submerged in theelectroless copper bath, the Walls surrounding the holes also received auniform adherent deposit of electroless copper.

As will be clear, the technique described in this example is suitable tomake printed circuits on both sides of an insulating panel with platedthrough holes directly. Heretofore, great difficulty has beenexperienced in the trade in making plated through holes usingelectroless deposition techniques. The procedure outlined in Example 25as well as certain of the other examples contained herein, represents asignificant advancement in the art of making plated through holes.

If desired, special properties may be imparted to the copper conductingpatterns produced as disclosed herein, as for example by depositingnickel, gold, silver, rhodium, and similar metals on the copperconducting pattern in whole or in part.

Typical nickel baths which may be used to deposit the additional metalsare described in Brenner, Metal Finishing, 1954, pp. 68 to 76, andcomprise acidic aqueous solutions of a nickel salt, such as nickelchloride; an active chemical reducing agent for the nickel salt, such asa hypophosphite; and a complexing agent, such as carboxylic acid andsalts thereof. Suitable electroless gold plating baths which may be usedto deposit additional metal are disclosed in U.S. Patent 2,976,181, andcontain a slightly water soluble gold salt, such as gold cyanide, areducing agent for the gold salt, such as the hypophosphite ion, and achelating or complexing agent, such as sodium and potassium cyanide. Thehypophosphite ion may be introduced in the form of hypophosphorous acidand salts thereof, such as sodium, calcium and ammonium salts.

It should be clear from the foregoing examples that when the embodimentusing the adhesive resin is employed, printed circuits may be made byemploying either the direct or.reverse printing technique. Also,following formation of the conductor pattern, the copper circuit can bedip soldered in whole or in part. If only portionsofthe circuit are tobe dip soldered, a permanent or non-permanent solder mask may be used tocoat the conductor pat: tern prior to dip soldering. Also, if desired,the conduct ing copper pattern, either in whole or in part, may receivean additional coating of metal, such as gold, silver, rhodium and thelike, to impart special properties to the circuit as a whole ordesignated portions thereof.

It should also be clear fromthe foregoing that com; pleted circuits withplated through .holes can be readily and facilely made according to thetechniquesdis'closed herein, including modifications of such techniqueswhich will be obvious to those skilled in the art. 7

The invention in its broader aspects is not limited tothe' specificsteps, methods, compositions and improvements shown and describedherein, but departures may be made within the scope of the accompanyingclaims without de parting from the principles of the invention andwithout sacrificing its chief advantages.

What is claimed:

1. An article of manufacture comprising an insulating resinous basehaving dispersed throughout said base an agent catalytic to thereception of electroless metal, said insulating resinous base containingat least one hole, .said catalytic agent being exposed at the surface ofthe wall surrounding said hole and said base on the wall surroundingsaid hole having strongly adhered thereto a layer of electrolesslydeposited metal.

2. An article of manufacture comprising an insulating resinous basehaving a metal layer adhered to at least one surface thereof and havingdispersed throughout said base an agent catalytic to the receptionofelectroless metal, said base containing at least one hole, saidcatalytic agent being exposed at the surface of the wall surroundingsaid hole, and said base on the wall surrounding said hole havingstrongly adhered thereto a layer of electrolessly de-, posited metal. I

3. An article of manufacture comprising an insulating resinous basehaving dispersed throughout saidbase an agent catalytic to the receptionof electroless copper, said base containing at least one hole, saidcatalytic agent being exposed at the surface of the wall surroundingsaid hole, and said base on the wall surrounding said hole havingstrongly adhered thereto a layer of bright, ductile, electrolesslydeposited copper.

4. An article of manufacture comprising an insulating resinous basehaving ametal layer adhered to at least one surface thereof and havingdispersed throughout said base an agent catalytic to the reception ofelectroless copper, said base containing at least one hole, saidcatalytic agent being exposed at the surface of the wall surroundingsaid hole, and said base on the wall surrounding said hole havingstrongly adhered thereto a layer of bright, ductile, electrolesslydeposited copper. h

5. An article of manufacture comprising an insulating resinous basehaving a copper layer adhered to at least one surface thereof and havingdispersed throughout said base an agent catalytic to the reception ofelectroless copper,

said base containing at least one hole, said catalytic agent 1 beingexposed at the surface of the wall surrounding said hole, and said baseon the wall surrounding said hole having strongly adhered thereto alayer of bright, ductile,

electrolessly deposited copper.

' 6. A printed circuit board comprising an insulating resinous basehaving a metal layer adhered to at least one" surface thereof, andhaving dispersed throughout said base an agent catalytic to thereception of electroless metal, said base containing holes at pointsdefining cross-overs be-* tween the top and bottom surfaces of the base,said catalytic agent being exposed at the surface of the wallssurrounding said holes, and said base on the walls surrounding saidholes havingstrongly adhered theretoa layer of electrolessly depositedmetal. v f

7. A printed circuit board comprising: an insulating resinous basehaving dispersed throughout said base an agentcatalytic-to the receptionof electroless copper, said base containing holes at points definingcross-overs between the topand bottom surfaces of the base, saidcatalytic agent being exposed at the surface of the walls surroundingsaid holes, and said base on the walls surrounding said holes havingstrongly adhered"theretoa'layerof bright, ductile, electrolesslydeposited copper.

8. A printed circuit board comprising an insulating resinous base havinga metal layer adhered to at least one surface thereof and havingdispersed throughout said base an agent catalytic to the reception ofelectroless copper, said base containing holes at points definingcross-overs between the top and bottom surfaces of the base, saidcatalytic agent being exposed at the surface of the walls surroundingsaid holes, and said base on the walls surrounding said holes havingstrongly adhered thereto a layer of bright, ductile, electrolesslydeposited copper.

9. A printed circuit board comprising an insulating resinous base havinga copper layer adhered to at least one surface thereof and havingdispersed throughout said base an agent catalytic to the reception ofelectroless copper, said base containing holes at points definingcrossovers between the top and bottom surfaces of the base, saidcatalytic agent being exposed at the surface of the walls surroundingsaid holes, and said base on the walls surrounding said holes havingstrongly adhered thereto a layer of bright, ductile, electrolesslydeposited copper.

10. A printed circuit board comprising an insulating resinous basehaving a resinous layer on at least one surface of said base, said basehaving dispersed throughout said base an agent catalytic to thereception of electroless copper, said resinous layer having dispersedtherein an agent catalytic to the reception of electroless copper, saidbase containing holes at points defining cross-overs between the top andbottom surfaces of the base, said catalytic agent of said resinous basebeing exposed on the surface of the walls surrounding said holes, andsaid base on the walls surrounding said holes having strongly adheredthereto a layer of bright, ductile, electrolessly deposited copper.

11. A printed circuit board comprising an insulating resinous basehaving a resinous layer on at least one surface of said base, said basehaving dispersed throughout said base an agent catalytic to thereception of electroless metal, said resinous layer having dispersedtherein an agent catalytic to the reception of electroless metal, saidbase containing holes at points defining cross-overs between the top andbottom surfaces of the base, said catalytic agent of said resinous layerbeing exposed on at least a portion of the surface of said layer, saidcatalytic agent of said resinous base being exposed on the surface ofthe walls surrounding said holes, said resinous layer on the surfacewhere said catalytic agent is exposed having strongly adhered thereto alayer of electrolessly deposited metal, and said base on the wallssurrounding said holes having strongly adhered thereto a layer ofelectrolessly deposited metal.

12. A printed circuit board comprising an insulating resinous basehaving a resinous layer on at least one surface of said base, said basehaving dispersed throughout said base an agent catalytic to thereception of electroless copper, said resinous layer having dispersedtherein an agent catalytic to the reception of electroless copper, saidbase containing holes at points defining cross-overs between the top andbottom surfaces of the base, said catalytic agent of said resinous layerbeing exposed on at least a portion of the surface of said layer, saidcatalytic agent of said resinous base being exposed on the surface ofthe walls surrounding said holes, said resinous layer on the surfacewhere said catalytic agent is exposed having strongly adhered thereto alayer of bright, ductile, electrolessly deposited copper, and said baseon the walls sur- 18 t rounding said holes having strongly adheredthereto a layer of bright, ductile, electrolessly deposited copper. 13.A printed circuit board comprising aninsulating resinous base having aresinous layer on at least one surface of said base, said base havingdispersed throughout said base an agent catalytic to the reception ofelectroless copper, said resinous layer having dispersed therein anagent catalytic to the reception of electroless copper, said resinouslayer containing a mask leaving exposed an area outlining a printedcircuit pattern, said base containing holes at points definingcross-overs between the top and bottom surfaces of the base, saidcatalytic agent of said resinous layer being exposed on the surface ofsaid layer forming said pattern, said catalytic agent of said resinousbase being exposed on the surface of the walls surrounding said holes,said resinous layer on the surface where said catalytic agent is exposedhaving strongly adhered thereto a layer of bright, ductile,electrolessly deposited copper, and said base on the walls surroundingsaid holes having strongly adhered thereto a layer of bright, ductile,electrolessly deposited copper.

14. A printed circuit board comprising an insulating resinous basehaving a resinous layer on at least one surface of said base, said layerforming a printed circuit pattern; said base having dispersed throughoutsaid base an agent catalytic to the reception of electroless copper,said resinous layer having dispersed therein an agent catalytic to thereception of electroless copper, said base containing holes at pointsdefining cross-overs between the top and bottom surfaces of the base,said catalytic agent of said resinous layer being exposed on the surfaceof said pattern, said catalytic agent of said resinous base beingexposed on the surface of the walls surrounding said holes, saidresinous layer having strongly adhered thereto a layer of bright,ductile, electrolessly deposited copper, and said base on the wallssurrounding said holes having strongly adhered thereto a layer ofbright, ductile, electrolessly deposited copper.

15. An article of manufacture comprising an insulating resinous base,having a resinous layer on at least one surface of said base saidresinous layer having a copper layer adhered thereto, said resinouslayer having dispersed therein an agent catalytic to the reception ofelectroless copper, and said base having dispersed throughout said basean agent catalytic to the reception of electroless copper.

16. A printed circuit board comprising an insulating resinous basehaving a resinous layer on at least one surface of said base, saidresinous layer having a metal layer adhered thereto, said resinous layerhaving dispersed therein an agent catalytic to the reception ofelectroless copper, said base having dispersed throughout said base anagent catalytic to electroless copper, said base containing holes atpoints defining cross-overs between the top and bottom surfaces of thebase, said catalytic agent being exposed at the surface of the wallssurrounding said holes, and said base on the walls surrounding saidholes having strongly adhered thereto a layer of bright, ductile,electrolessly deposited copper.

17. A printed circuit board comprising an insulating resinous basehaving a resinous layer on at least one surface of said base, saidresinous layer having a copper layer adhered thereto, said resinouslayer having dispersed therein an agent catalytic to the reception ofelectroless copper, said base having dispersed throughout said base anagent catalytic to electroless copper, said base containing holes atpoints defining cross-overs between the top and bottom surfaces of thebase, said catalytic agent being exposed at the surface of the wallssurrounding said holes, and said base on the walls surrounding saidholes having strongly adhered thereto a layer of bright, ductile,electrolessly deposited copper.

18. A three-dimensional article comprising an insulating resinous basehaving dispersed throughout said base an agent catalytic to thereception of electroless metal, said base having interconnectinginternal channels which define circuit patterns, said catalytic agentbeing exposed on the walls defining thev channels, ands aid base havingon the walls defining the channels, where said catalytic agent isjexpese'd, alayer' of lectrolessly deposited metal strong- 1y adheredthe r e t o. I

I References Cited I UNITED STATES PATENTS 2,897,409 7/1959 Gitto3177-101 2,943,956 j 7/1950 Robinson 1 17l 212 10 3,031,344 4/1962 She:etal. 117-212 3,134,690 5/1964 Eriks s'on 117- 213 3,165,672 1/1965. Gellert 317;100 3,202,591 I 8/1965. Curran. '204--38 3,119,709 I 1/1964Atkinson -117+-47 2,690,401 9/19 54 Gut zeiteta1. 11747 2,690,403 9/1954Gutzeit et a1. 117 47 3,171,756 3/1965 Marsha1l 117-212 WILLIAM L;JARyIS,-;Primary Examiner. s

